THE EOCENE SEltlKS 531 



(30 to 40 feet), and both beds contain many fossils (see p. 529) ; 

 tin- lirst i-xjMMiiv is in tin- rl ill's of Pegwell Bay near Rainsgate, 

 and this is illustrated in Fig. 182. It is also seen at Reculvers 

 mi tin- north coast of Kent. Westward the sandy marl passes into 

 tini- soft pale-green or buff sand (argillaceous at the base), while 

 tin- upper sands appear to thin out, so that in the west of Kent 

 the whole is not more than 50 feet thick ; this type of the Thanet 

 Beds is well exposed in the pits near Woolwich and Charlton, but 

 contains no fossils. Thence the outcrop runs by Crayford and 

 Croydoii to Epsom, where the sands are only 15 feet thick, thinning 

 out entirely near Ashstead. 1 



The Thanet Beds thin northward as well as westward, for 

 though well-sections at Chelmsibrd and Braintree show them to be 

 about 30 feet thick, at their outcrop near Sudbury they are only 

 16 feet, and they thin out to the west near Gestingthorpe. 



The "Woolwich, Beading, and Oldhaven Beds. These 

 form a much more variable group, and exhibit three different facies as 

 they are traced from east to west : (1) the marine type, consisting 

 of grey sands with marine shells, is only found in East Kent ; (2) 

 the estuarine or Woolivich type occurs in West Kent and East 

 Surrey, and consists of sands, clays, and pebble beds, with estuarine 

 and freshwater shells ; (3) the Reading type of the western and 

 northern tracts consists of unfossiliferous variegated plastic clays 

 and bright- colon red sands. 



Overlying the marine and estuarine beds of the Woolwich Group 

 in Kent and Surrey are pebbly sands and pebble beds, from 10 

 to 50 feet thick, which are termed the Oldhaven or Blackheath Beds 

 by Mr. Whitaker, and are grouped by him as a third division of the 

 Lower London Tertiaries. Their stratigraphical extent, however, 

 is not great, and their palauontological importance is small, so that 

 they hardly seem entitled to rank as a primary division. 



The coast near Reculvers in Kent furnishes a good section of the 

 marine type of this group, and is as follows : 



Feet 

 Oldhaven Beds. Grey and buff sands, hardened in places into a 



ferruginous sandstone ; a layer of pebbles at base ... 20 

 Woolwich Beds. Pale-grey sand with sharks' teeth, Corbula 



regulbiensif, Protocardium Laytoni, Cyprina Morrisi, etc. . 25 



Near Milton estuarine beds conic in in-ar the middle of the 

 Woolwich Beds, and at Upnor on the Medway there are 6 feet of 

 clay with brackish-water fossils intercalated in the pale-grey sands. 



At Woolwich the greater part of the beds are estuarine clays 

 and sands, in which Melania inquinata, Potamides funatus, and 

 Cyrena cuneiformis are common fossils. Resting on an eroded 



